physical and chemical properties and efforts will also be made to iden- 

 tify its various cleavage products. 



Animal Experiments.— Numerous tests have already been made in 

 order to establish the exact rabbit unitage of the crystalline compound. 

 The rabbit unit employed by us is that fraction of a milligram per 

 kilogram of body weight which will cause convulsions or lower the 

 blood sugar to 0.045 per cent within 5 hours. This corresponds to ap- 

 proximately IV2 times the "clinical unit" used at present. 



The exact dosage of the crystalline material has not yet been estab- 

 lished, but for the present, as is shown in the subjoined table (1), 

 amounts as small asi^Qgof a milligram per kilo lowered the blood 



TABLE 1 



Blood Sugar Determinations 



Insulin crystals dissolved in M/15 Na2HP04 . 

 1 mgm. equivalent to 10 cc. solution. 

 Injections were made subcutaneously. 



" As defined in the text. 



sugar to about the convulsive level, 0.045 per cent. In another series of 

 experiments 1^25*^^ ^ milligram per kilo produced convulsions in one 

 rabbit and lowered the blood sugar almost to the convulsive level in a 

 second animal. (Table 2.) It wall be clear, therefore, that we are deal- 

 ing here with a hormone which, in very high dilution, influences car- 

 bohydrate metabolism acting as it were like a catalyst in a chemical 

 reaction. 



With the isolation of this hormone in crystalline forin we are leav- 

 ing the region of qualitative experiments, and may look forward to 

 cpiantitative results both in the biological and chemical field which 

 the future promises to yield. 



79 



